<!--
 * @Author: coman
 * @LastEditors: coman
 * @Date: 2020-06-10 12:12:00
 * @motto: No pain,No gain
 * @LastEditTime: 2020-06-10 12:59:33
--> 
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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var flag=1;
        var sum =0;
       /*  2、求出1-1/2 + 1/3 - 1/4 + 1/5....... 1/100的和 */
       for(var i=1;i<=100;i++){
            sum=sum+flag*1/i;
            flag=-flag;
       }    
       console.log("总和为:"+sum);
       

    </script>
</body>
</html>